1. Field of the Invention
The present invention relates to furniture assemblies and particularly to an assembly of rods, caps, posts and panels providing a rigid furniture structure. More particularly, the the present invention relates to assemblys of tables, utility carts, cabinets, chests, desks, beds, self-supporting shelving, room dividers and multi-functional wall systems which may be assembled by the factory or by an end user using interlocking part-to-part joining of panels, posts, threaded rods and caps to provide a rigid furniture structure that does not entail the use of tools or conventional hardware fasteners, conventional part-to-part joining or adhesives.
2. Description of the Prior Art
Assembling most conventional factory furniture entails the use of a variety of hardware connectors, including nails, staples, screws, nuts, bolts, washers, brackets and tension rods, in combination with pinned, dowelled, wedged, splined, dovetailed, dadoed or braced part-to-part connections that are glued to secure their permanence.
Standard furniture practice for assembling legs to, for example, table tops calls for the use of steel or wooden angle brackets that are secured to a leg as well as to a pair of wooden rails that meet the leg at right angles. Sometimes the rails are dowelled and glued directly into the leg. These rails are in turn fastened to a top by means of screwed angles, glued and screwed wedges, or screws directly through the rails into the top, or by means of some combination of these techniques. The unsightliness of these connections requires that they be hidden from view. This is usually accomplished by using the rail, which is structurally connected to the leg, as a decorative skirt that wraps around and conceals all the unsightly connections from view. Where side or back panels are required in, for example, desks or chests, (either in lieu of legs or as a fill-in between leg framing elements) they are usually joined to each other, or to frames or tops, by means of screwed angle brackets or screwed and glued wedges. Since these connections are usually inside the desk or chest they are not seen, and thus no unusual effort is required to prevent their view. On the outside, veneers of plastic or wood, and various moldings, are used extensively to cover or disguise exterior joints and interstices between parts that are considered unattractive.
Further, conventional factory assembled furniture is generally designed for the performance of an exclusive furniture function that cannot generally be modified by the adding or taking away of accessory parts.
Still further, systems for knock-down assembly either in a factory or by an end user generally must deal with connective devices and techniques more discreetly and more selectively than is the case with conventional factory assembled furniture. This is because the objective of easy assembly as a primary consideration in knock-down furniture design encourages sparse, bare-boned structural solutions that aim at a minimum of parts and are largely devoid of cosmetically decorative elements that in conventional furniture serves to conceal or disguise the unsightly details of assembly. Accordingly, knock-down furniture systems tend to rely heavily upon connecting hardware devices that are designed for discreet concealment within the members to be joined. The members are provided with countersunk openings to receive fastening devices, which are generally comprised of screws, slots, nuts, bolts, steel rods and cams in various configurations. In some configurations the exterior ends of hardware linkages are left exposed in countersunk openings which may or may not be capped. In other configurations the hardware is almost entirely concealed within the interfacing surfaces of the parts joined.
Direct part-to-part joining techniques that do not require hardware are not generally incorporated in furniture systems that are designed for knock-down assembly. This is because conventional interlocking part-to-part joining techniques without hardware generally require the use of glue. Glueing techniques generally require clamping under controlled conditions to insure proper bonding.
Additionally, glued joints are not desirable for knock-down furniture because end users prefer knock-down systems that do not entail potentially messy and tricky glued connections. Nevertheless, while most conventional knock-down furniture assembly systems rely upon hardware fasteners and not interlocking part-to-part joining techniques, the achievement of a rigid and easily assembled interlocking part-to-part knock-down system requiring little or no hardware has been a goal of many designers and inventors, with various efforts in that direction being made.
One known assembly consists of combinations of tubular or rod-like framing members with various interconnecting corner members for the construction of three dimensional cubic frameworks. Since side, top and back panels are required for specific furniture functions, functional elements are generally clipped non-rigidly to the scaffold-like framework by means of accessory hardware devices. The application of part-to-part joining in these systems is limited only to the framework, which in terms of furniture function has none.
A consequence of the absence of rigid part-to-part interlocking between panels and framework in these systems is that a panel's contribution to the rigidity of a structure can be no greater than the strength of the device that clips it to the structure. Accordingly, these systems depend entirely on the integrity of their rod-to-corner piece joining for their rigidity. This means very extreme tolerance requirements in the manufacture of these parts. It also means that these parts require skilled installers for proper assembly and disassembly. Hence, even though these systems assemble and disassemble at the point of use, they cannot be properly termed knock-down systems, since that term implies assembly or disassembly by the the user.
Other efforts to obtain interlocking part-to-part knock-down assembly systems which require little if any hardware fasteners focus on the use of spindles and shelves to create vertical arrays of shelves, see for example, U.S. Pat. Nos. 3,831,533 and 4,099,472 to Kellog. In these systems the spindles extend vertically between shelves to hold them in spaced relationship to each other. It is common in these systems to provide the spindles with reciprocal male and female threaded ends, or to combine female threaded ends on the spindles with male threaded connectors, which when engaged through openings in a shelf will secure the shelf in a position between themselves. Since the part-to-part interlock of shelf to spindle is limited in such a system to the spindle ends, where the spindles act essentially as nut and bolt in sandwiching shelves between themselves, the spindles and shelves receive no mutual reinforcement from each other in resisting the system's susceptibility to torsion stresses that would make it twist and sway. Accordingly, the system's resistance to torsion forces is dependent entirely upon the rigidity of the spindles, which must be of considerable thickness as a consequence, and upon the tightness of the spindle-to-spindle and spindle-to-shelf interlock. Because these parts are usually made of materials that are dimensionally unstable in climatic changes, and very tight fits of spindle ends through shelf openings would impair ease of knock-down assembly, the parts cannot be manufactured to tolerances that are too exacting. Thus these systems exhibit a tendency to swing and sway to a degree that would not normally be tolerated in factory assembled furniture having a similar function.
Another prior art knock-down furniture assembly which utilizes a minimum of hardware fasteners is described in U.S. Pat. No. 3,570,418 to Gooding et al. This assembly includes two vertical side supports having slots for receiving tongues at the ends of transverse boards, and holes for receiving dowel screws which fit into the ends of support rails. The rails are secured to the side supports by knobs fastened onto the outer ends of the dowel screws. Gooding et al utilizes the spindle/shelf structure turned on its side so that what were shelves in the Kellog systems are now functional as vertical supports, and what were vertical spindles in the in the Kellog systems now serve as horizontal spacing members between those supports. Since what were horizontal shelves in the Kellog systems have now been transformed into vertical supports, a new element is introduced to function as a horizontal surface. While this horizontal surface is parallel to the spindles that hold the array together, it is not interlocked with the spindles in any manner for strengthening the system's resistance to loading forces that would cause it to sway and bend out of square alignment as a result of any weakness or looseness in the interlock between the spindles and caps that sandwich the vertical supports in nut and bolt fashion. This critical linkage is recognized as a potential weak point in the Gooding et al system, and Gooding et al introduces washers to assist in obtaining a tight cap vertical support/spindle sandwich. The horizontal panel, is linked to the vertical supports by means of tabs that extend from its ends through slots in the vertical supports. This loose linkage, however, is not locked in any way for the purpose of strengthening the system's rigidity, and serves simply to hang the horizontal member in place.
Another modification in Gooding et al and to Kellog relates to the threaded interlock between spindles and caps. Both spindle ends are fitted with female threading. An additional part in the form of a male threaded dowel is required to make the spindle-to-cap interlock. The introduction of this third part in the interlock configuration contributes to problems in tightening the interlock and maintaining its rigidity, the problematical nature of which is attested to by the need for washers, since spindle and cap are each now fitted to an intermediate part instead of directly to each other.
In further recognition of this rigidity problem Gooding et al requires that at least three spindles be used to secure the vertical supports for adequate rigidity. These spindles must be spaced in a vertical direction as well as laterally. As a consequence the third spindle, in its location at midpoint between the top and bottom of the vertical supports, is potentially a functional encumbrance in some applications of the system, as for instance, in desk or table configurations.
Nevertheless, with regard to function, this system seems to describe some advantages over the previously discussed Kellog vertical spindle arrays. Kellog does not describe functional modification. Kellog makes no provision for the insertion of side or rear panels between a pair of shelves for transformation of an open segment into a chest or cabinet. On the other hand, the horizontal spindle array does describe some functional modification. This modification, however, cannot be achieved by the addition or substraction of parts that will transform a given unit from one functional role to another. The total replacement of discreet functional subassemblies is required to achieve modification of function.
The use of horizontal rods or rails fitting into recesses and holes in vertical legs to form a chair is also known, as shown in U.S. Pat. No. 233,478 to Creager. In this case, the front legs and seat are preassembled and the rear legs and back connected permanently. A rear rail is beveled at each end to fit snugly into angular recesses in the back to support the seat. Side rails include shoulders and projections at the rear ends to fit into holes in the back and to be flush with the back when secured. The projections are split and the ends for the insertion of wedges which fit into countersunk apertures to hold the assembly together.
These known structures, however, are not sufficiently rigid and the elements tend to move out of alignment and become displaced and unsteady.
Of additional interest are the following U.S. Patents:
U.S. Pat. No. Des. 27,227 to Zinn;
U.S. Pat. No. 115,456 to Fisher;
U.S. Pat. No. Des. 252,719 to Otero;
U.S. Pat. No. 719,837 to Morton;
U.S. Pat. No. 3,097,615 to Ross;
U.S. Pat. No. 3,131,970 to McGregor;
U.S. Pat. No. 3,743,353 to Lupinsky;
U.S. Pat. No. 3,880,095 to Clark et al; and
U.S. Pat. No. 4,261,667 to Ervin et al.